Bonding surfaces with two-component adhesive of epoxy resins and amine compound

Abstract

The present invention relates to a two-component epoxy adhesive composition comprising a) a first component comprising a first epoxy resin and a second epoxy resin, the second epoxy resin being flexibilized by an elastomer, and b) a second component comprising at least one amine compound with one or more primary and/or secondary amino groups, said amine compound having a molecular weight of less than 450 g/mol. The ratio of the total number of amino groups of the amine compound to the total number of epoxy groups of the epoxy resins is 0.01:1 to 0.5:1. The mixing of the two components a) and b) results in a wash-off resistant composition. Said wash-off resistant composition results upon heat-curing in a crash-stable structural adhesive.

1. A process for bonding together separate surfaces comprising mixing component a) and component b) of a two-component epoxy adhesive composition comprising
 a) a first component comprising a first epoxy resin and a second epoxy resin, the second epoxy resin being flexibilized by an elastomer, and 
 b) a second component comprising at least one amine compound with one or more primary and/or secondary amino groups, said amine compound having a molecular weight of less than about 450 g/mol,
 wherein the weight ratio of the first component a) to the second component b) is from about 2:1 to about 10:1, the ratio of the total number of amino groups of the amine compound to the total number of epoxy groups of the epoxy resins is from about 0.06:1 to about 0.2:1; 
 
 applying the resulting mixture to at least one surface, bringing together the surfaces and curing the epoxy adhesive composition between the surfaces at a temperature above about 120° C. for at least about 10 minutes. 
 
     
     
       2. A process according to  claim 1  wherein the epoxy adhesive composition is cured at a temperature above about 140° C. for at least about 20 minutes. 
     
     
       3. A process according to  claim 1 , wherein the epoxy adhesive composition is cured up to about 4 weeks after bringing together the surfaces. 
     
     
       4. A process according to  claim 1 , wherein the amine compound is selected from the group consisting of 4,7,10-trioxatridecan-1,13-diamine, diethylenetriamine, triethylenetetramine tetraethylenepentamine, aminoethylpiperazine, polyetherdiamines and polyethertriamines. 
     
     
       5. A process according to  claim 4 , wherein at least one of the two components a) and b) comprises a toughener. 
     
     
       6. A process according to  claim 5 , wherein the toughener is selected from the group consisting of compounds of Formula I 
       
         
           
           
               
               
           
         
       
       wherein m is 1 or 2, n is 2 to 6, R 1 is an n-valent radical of an elastomeric prepolymer after the removal of the terminal isocyanate, amino or hydroxyl group, the elastomeric prepolymer being soluble or dispersible in epoxy resin, W and X are independently—O—or —NR 3 —, at least one of W and X being —NR 3 —, R 2  is an m+1-valent radical of a polyphenol or aminophenol after the removal of the phenolic hydroxyl group and optionally of the amino group, and R 3  is hydrogen, a C 1 -C 6  alkyl or phenol, and compounds of Formula II 
       
         
           
           
               
               
           
         
       
       wherein p is 1 or 2, q is 2 to 6, Y is —O—, —S—or —NR 6 —, Z is a radical selected from the group consisting of —OH, —NHR 6 , —OCN, 
       
         
           
           
               
               
           
         
       
       R 4  is a residue of a hydroxyl-, mercapto- or amino-terminated polyether prepolymer or of a hydroxyl-, mercapto- or amino-terminated prepolymeric, segmented polyester, polythioester or polyamide, R 5  is a carbocyclic aromatic or araliphatic p+1-valent radical with groups Z bonded directly to the aromatic ring, R 6  is hydrogen, C 1 -C 6  alkyl or phenyl, and R 7  is methyl or hydrogen, or a mixture thereof. 
     
     
       7. A process according to  claim 1 , wherein the elastomer flexibilizing the second epoxy resin is an acrylonitrile-butadiene rubber. 
     
     
       8. A process according to  claim 1 , wherein at least one of the two components a) and b) comprises a latent hardener in a total amount of less than about 10 weight percent based on the total weight of the composition. 
     
     
       9. A process according to  claim 8 , the latent hardener being dicyandiamide. 
     
     
       10. A process according to  claim 1 , wherein the second component b) comprises a hydrophobic diluent. 
     
     
       11. A process according to  claim 1 , wherein at least one of the two components a) and b) comprises one or more additives selected from the group of latent accelerators, adhesion promoters, epoxy silane, fumed silica, wetting agents and inorganic fillers. 
     
     
       12. A process according to  claim 1  wherein at least one of the two components a) and b) comprises at least one tertiary mono- or polyamine or a mixture thereof as accelerator, the tertiary mono- or polyamine being embedded in a polymer matrix if comprised in component a). 
     
     
       13. A process according to  claim 5 , wherein
 a) the first component comprises from about 30 to about 80 weight percent of the first epoxy resin, from about 5 to about 30 weight percent of the second epoxy resin and about 20 weight percent or less of the toughener, 
 b) the second component comprises from about 1 to about 40 weight percent of the amine compound, from about 10 to about 80 weight percent of the toughener and from about 10 to about 30 weight percent of the hydrophobic diluent, 
 and at least one of the two components a) and b) comprises an inorganic filler, epoxy silane, a wetting agent, fumed silica, a latent hardener, a latent accelerator or a mixture thereof.